repetitive front main seal leakage

[supraguru05]

Alright this is a pretty complicated problem and I will try to make the situation as clear as possible. The car is a 1989 supra with a rebuilt NA-T with full turbo electronics. it has a turbo oil pump that is shimmed, a full flow oil cooler system, stock ct26 turbo. This is my race car and the engine was rebuilt a year ago and has had no problems. this winter i wanted to fix a tiny coolant leak from one of the gaskets behind the timing cover so i removed the timing cover replaced the gaskets and put it back on with sealant on top so it would seal against the head gasket. I also at this time swapped in a turbo oil pump and shimmed the pump. also i added a crank scrapper. after putting it all back together it ran fine and had no leaks. i ran it for about 50 miles with no problems then painted the car. during the painting i installed a new dipstick that seals tightly unlike the pervious dipstick that leaked air. i installed a new diff and had the car jacked up and when i was running the car on jack stands to get the diff lubbed up it started dripping oil out of the front most timing cover. immediately i think did i replace the main seal, i dont think i did so i assume the seal is just bad because it is old. I replace the main seal with a new one. restart and the same thing happens. now im thinking its because i pulled the timing cover off, after using UV dye it is leaking from the seal around the crank not from the head area. my thoughts are that i am pushing the main seal out due to poor crank case ventilation. i put the car on the ground restart and the leak disappears. at this point my dad belives the leak was because the car had its nose pitched down at a angle, i disagree. currently the car doesnt leak but im trying to figure out what the problem could be. my plan is to replace the outlets of the valve covers with 1/2 npt ports, and in an effort to reduce the high cold start up oil pressure i am going to switch back to 0w-30 oil. currently running 5w-30. any ideas?


cliff notes

repeat main seal leak with car slightly pitched down in the front.

possible failures
high blowby (upgrading cam cover outlet sizes)
high cold start oil pressure (60-80psi) (fix is switch oil weight)
bent crank??
bad timing pulley?

any other ideas are appreciated. this car is well maintained and doesnt have clogged pvc orifices, however it does have what i believe to be a blown front turbo seal.

 

[3p141592654]

Oil pressure plays no role in a front crank seal leak.Most likely, replacing the dipstick with one that sealed better raised your crankcase pressure and that created a leak at the next weakest point which apparently was your front crank seal.

1) Your PCV should be setup like a stock turbo with the vent going to the intake manifold and the accordion. Provide more details on your PCV setup, and search the forum because this topic has been beaten to death

2) Your engine may be just worn out and the excessive blowby is overwhelming your PCV setup raising the crankcase pressure to the point where the weakest seal leaks.

3) The seal may have worn a groove in the crank causing it not seal properly, even with a new seal. That will require a machinist's help to fix. If you think the crank nose is bent put a dial indicator on it and rotate the crank to check.

 

[supraguru05]

Oil pressure plays no role in a front crank seal leak.Most likely, replacing the dipstick with one that sealed better raised your crankcase pressure and that created a leak at the next weakest point which apparently was your front crank seal.

1) Your PCV should be setup like a stock turbo with the vent going to the intake manifold and the accordion. Provide more details on your PCV setup, and search the forum because this topic has been beaten to death

2) Your engine may be just worn out and the excessive blowby is overwhelming your PCV setup raising the crankcase pressure to the point where the weakest seal leaks.

3) The seal may have worn a groove in the crank causing it not seal properly, even with a new seal. That will require a machinist's help to fix. If you think the crank nose is bent put a dial indicator on it and rotate the crank to check.

thanks for the information as far as the search im no amature and ive been around long enough to know the common failure modes. the pvc system is setup exactly as stock with everything in good repair. i did a compression test and the compression was even across the board however i have concerns about the rings in cylinder 3 due to burned oil on the spark plug asfter the race. i haven't sourced a leak down tester yet to verify. i was unaware that the rubber seal could groove the metal pulley, thats the information i was looking for. I will be switching out the crank pulley saturday

 

[3p141592654]

I forgot that the front crank seal rides on the crank timing-belt pulley. That is very convenient as you can change it out easily if grooved. Also, there was a discussion a long time ago about the fact that there is no o-ring seal between the pulley and the crank nose, so that oil, in theory at least, could leak through the gap. Some of those pulleys are a real tight fit, and others like mine slide off with no effort. You might put a bit of FIPG on the nose before sliding the pulley on to seal that up if yours is a loose fit like mine.

Yup, a rubber seal can wear a groove in hardened steel. I had a persistent leak in my differential side seal. Replaced the seal three times thinking I had messed up the install. There was a barely noticeable groove in the half shaft that I figured could not cause any problem, but in the end, it was enough to be the cause of the leak.

 

[supraguru05]

bought a new seal and my dad found a spare timing sprocket and it pops into the seal instead of sliding like my current one. so im hoping this is the issue should have it resolved Saturday, then i just have to make sure i rebuilt the differential right

 

[jdub]

To add, tilting the engine forward may have put liquid oil in contact with the seal vs the normal windage vapor...so, your Dad has the right idea. Crankcase pressure could have forced some past the seal per the info posted.

I like to use a seal shellac (like Indian head) on the outside edge of a crank/cam seal. Makes installing it easier and it prevents leaks. In the case of a grooved crank snout, not much you can do besides take it to a machinist. I always use Toyota seals.

 

[IJ.]

If the bottom pully isn't a snug fit on the crank you can get seepage past the pully along the keyway and into the lower timing cover.

A smear of RTV on assembly solves this one.

 

[grimreaper]

^^ my cams leak like this, just a ring around the snout where the seal is touching the metal?

 

[supraguru05]

well after thinking to myself to keep it simple i decided to dye check the engine again. after further inspection here is what i found.

as you can barely see there is some green underneath the oil pump driveshaft seal. not clear in the pics but able to be seen in person is a light green trail running straight down from the seal. upon removal of that seal about 60 degrees of the inner lip was bent outward and didnt seat when i installed it over the winter. this was the root cause all along. the oil on the main seal and crank sprocket was due to it turn in the pool on the bottom of the timing cover. so problem fixed and thanks everyone for you help. this UV dye rocks and im going to run it in all the fluids i can now to check for all those little leaks that bug me. going racing tommorrow morning :evil2:

 

[jdub]

Great pics! Glad you found it

 

[Poodles]

Those pics are trippy

 

[jdub]

Uber cool IMO